The present invention relates to circuitized structures, and more particularly to composite circuitized structures such as printed circuit boards (PCBs). The present invention also relates to a method for fabricating such structures.
One method of forming a laminate circuitized board structure includes forming layers of dielectric material and electrically conducting material to provide multiple layers of circuits and voltage planes. Circuits can be discrete wiring patterns known as signal planes. Voltage planes can be either ground plane or power planes, and are sometimes collectively referred to as power planes. In one technique of forming such structures, layers of dielectric material and conductive material are successively applied, i.e., the dielectric material is applied and then circuits or voltage planes are provided thereon and, if necessary, through holes formed by drilling or etching. This method relies on each successive step of adding additional structure and the circuitry layers are formed individually, e.g., in each step in forming the plane having circuit traces or formed power planes. This requires precision drilling to form the plated through holes (PTHs) all of which is time consuming, especially where there is a large number of drilled holes required to form PTHs.
More recently, methods have been described that provide a relatively inexpensive photolithographic technique of forming a composite laminate structure (substrate assembly) from individual discrete laminate structures (substrates). For example, see U.S. application Ser. No. 09/812,261, entitled xe2x80x9cPrinted Wiring Board Structure With Z-Axis Interconnectionsxe2x80x9d and filed Mar. 19, 2001. See also U.S. Pat. No. 6,388,204 (Lauffer et al) and U.S. Pat. No. 6,479,093 (Lauffer et al), the teachings of which are incorporated herein by reference. Although the structures and methods of these inventions provide significant advances and advantages over current PCB fabrication methods, there still exists a need for further refinement. Therefore, continuing efforts are underway in attempting to provide for even greater advantages. The present invention is a result of such efforts.
It is believed that such an invention will constitute a significant advancement in the art.
It is a primary object of the present invention to enhance the circuitized substrate assembly art.
It is another object of the invention to provide a circuitized substrate assembly which provides for high density wiring patterns and which can be manufactured in an efficient, facile manner.
It is still another object of the invention to provide a method of making the aforementioned circuitized substrate assembly.
According to one aspect of the invention, there is provided a circuitized substrate assembly comprising a first circuitized substrate including an opening therein, a second circuitized substrate bonded to the first circuitized substrate and including an opening therein substantially aligned with the opening in the first circuitized substrate, and a quantity of electrically conductive paste substantially completely filling the opening in the second, bonded circuitized substrate and only partly filling the opening in the first circuitized substrate.
According to another aspect of the invention, there is provided a circuitized substrate assembly comprising a first circuitized substrate including an opening therein, a second circuitized substrate bonded to the first circuitized substrate and including an opening therein aligned with the opening in the first circuitized substrate, an electrically conductive cover member substantially covering the opening in the second circuitized substrate on the surface of the second circuitized substrate facing the first circuitized substrate, and a quantity of electrically conductive paste positioned on the cover member and only partly filling the opening in the first circuitized substrate.
According to yet another aspect of the invention, there is provided a method of making a circuitized substrate assembly comprising providing a first circuitized substrate including an opening therein, providing a second circuitized substrate including an opening therein, substantially filling the opening in the second circuitized substrate with a quantity of electrically conductive paste, aligning the first and second circuitized substrates such that the opening in the second circuitized substrate having the electrically conductive paste therein aligns with the opening in the first circuitized substrate, and bonding the first and second circuitized substrates together such that the electrically conductive paste only partly fills the opening in the first circuitized substrate while also substantially filling the opening in the second circuitized substrate.
According to still another aspect of the invention, there is provided a method of making a circuitized substrate assembly comprising providing a first circuitized substrate having an opening therein, providing a second circuitized substrate having an opening therein, positioning an electrically conductive cover member on a surface of the second circuitized substrate facing the first circuitized substrate to substantially cover the opening in the second circuitized substrate, positioning a quantity of electrically conductive paste on the cover member, aligning the first and second circuitized substrates such that the openings in the circuitized substrates are substantially aligned, and bonding the first and second circuitized substrates such that the quantity of electrically conductive paste only partly fills the opening in the first circuitized substrate.